For many years now cylinder head gaskets have been designed to employ armoring and wire rings at the combustion openings to facilitate sealing of the combustion cylinders. For many reasons, the sealing of combustion openings can be difficult to accomplish. A variety of techniques and types of armoring and wire rings have been employed to enhance the sealing effect of cylinder head gaskets at the combustion openings.
In recent times, the difficulty of sealing off combustion openings has increased, for example, in situations where bi-metallic engines, such as those having an aluminum cylinder head and a cast iron cylinder block, are used. Bi-metallic engines are inherently more difficult to seal than are all cast-iron engines, and they become even more difficult to seal when the cylinders are closely arrayed and where the cooling of localized zones of the cylinder head and cylinder block is relatively poor.
A variety of approaches to enhancing the sealing effect of head gaskets at combustion openings in bi-metallic engines have been attempted. Yet, the problems resulting from the use of bi-metallic and lighter weight engines still resist efforts at their elimination, and a need still remains for a sealing means that will resist over-compression, and yet will not so indent or imbed into the softer aluminum engine head that the seal fails, such as on start-up when the engine is cold, or under other conditions under which failures and leakage are too often encountered today.
Thus it would be desirable to provide a cylinder head gasket which requires minimum changes from conventionally used constructions, but which responds to the more difficult sealing requirements imposed by bi-metallic and lighter weight engines, such as those in which the cylinders are more closely arrayed and which are so structured that some localized overheating occurs, thereby threatening the integrity of the combustion seal.